Even though she was kidnapped by ISIS from a Doctors Without Borders vehicle, and had helped a friend install equipment at a Doctors Without Borders hospital in Syria, the prestigious humanitarian group refused to help negotiate for the freedom of American hostage Kayla Mueller, her parents tell ABC News.

Marsha and Carl Mueller of Prescott, Arizona, said the group refused to speak with them for months and then withheld critical information provided by freed Doctors Without Borders hostages -- information that directly concerned their daughter and was needed in order to begin negotiations for her release.

In a phone conversation recorded by the Muellers 10 months after their daughter's kidnapping and provided to ABC News, they asked the group if it would help negotiate for their daughter. "No," the senior official replied. "So, the crisis management team that we have installed for our five people and that managed the case for our people will be closed down in the next week. Yeah? ... Because our case is closed."

"They're a fabulous organization, and they do wonderful work," Carl Mueller told ABC News' "20/20" in an interview to be broadcast this Friday, "but somewhere in a boardroom, they decided to leave our daughter there to be tortured and raped and ultimately murdered."